The Surprising Bunts and Smuts“Still a threat after all these years”

James G. Menzies, AAFC, Winnipeg Manitoba

Denis Gaudet, AAFC, Lethbridge, Alberta

2

Bunt and Smut Pathogens of Barley, Oats and Wheat

Smut FungiBasidiomycetes

UstilaginalesTilletiaceae35 species

Important Species on the Prairie ProvincesUstilago spp. – Smut diseasesTilletia spp. – Bunt diseases

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Wheat Diseases

• Seedling Infecting Diseases

• Common Bunt• (Tilletia laevis, T. tritici)

• Dwarf Bunt (T. controversa)• Karnal Bunt (T. indica)

• Flag Smut (Urocystis agropyri)

• Floral or Embryo Infecting Disease

• Loose Smut (Ustilago tritici)

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Barley Diseases

• Seedling Infecting Diseases

• Covered Smut (U. hordei)False Loose Smut (U. nigra)

• Floral or Embryo Infecting Disease

• Loose Smut (Ustilago nuda)

5

Oat Diseases

• Seedling Infecting Diseases

• Covered Smut (U. kolleri)Loose Smut (U. avenae)

6

Worldwide Distribution of Common Bunt and Loose Smut

Wilcoxson and Saari, eds. 1996. Bunt and Smut Diseases of Wheat: Concepts and Methods of Disease Management. Mexico, D.F.: CIMMYT

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Life (Disease) Cycles of Seedling Infecting and Floral or Embryo Infecting Smut Fungi

Bailey, Gossen, Gugel and Morrall. 2003. Diseases of Field Crops in Canada. The Canadian Phytopathological Society.

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Conditions Affecting Loose Smut

• Favouring Development– Cool moist weather during flowering (95% RH, 20-25oC)– Conditions that extend the flowering of the host (more time to

infect).

• Detrimental to Development– Excessive heat and dry weather during flowering– Adverse environmental conditions during host development

may affect disease expression (i.e. low temperature).– Fusarium graminearum

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Conditions Affecting Common Bunt

• Favouring Development– Soil temperatures between 5 to 10oC– Infection can occur with soil moisture between permanent

wilting point and field capacity – optimum in the middle.– Deep seeding – as soil depth increases, the soil temperature

becomes more favourable for the pathogen.

• Detrimental to Development– Warm soil temperatures (infection is low at 22oC)– Other soil factors are not critical to disease development.

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Occurrence of Loose Smut of Wheat in Manitoba and Saskatchewan

0

10

20

30

40

50

60

70

80

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009Year

Perc

ent i

ncid

ence

hexaploid wheatdurum wheat

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Occurrence of Loose Smut of Barley in Manitoba and Saskatchewan

0

10

20

30

40

50

60

70

80

90

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009Year

Perc

ent i

ncid

ence

6 Row2 Row

12

Percentage Infection in Most Affected Fields –Manitoba and Saskatchewan

0

2

4

6

8

10

12

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009year

perc

ent h

ighe

st in

fect

ion

hexaploid wheatdurum wheat

13

Percentage Infection in Most Affected Fields –Manitoba and Saskatchewan

0

5

10

15

20

25

30

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Year

Perc

ent h

ighe

st in

fect

ion

6 row2 Row

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Symptoms of Loose Smut

• Smutted Spikes

• Narrow lines of sori on the flag leaf– More common in

barley

• Reduced tillers

• After heading, smutted plants may stop growing

Symptoms may not be readily visible at harvest.

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Symptoms of Common Bunt

• May not be apparent until after heading

• Immature infected spikes are darker green and remain green longer.

• Mature spikes are slightly lighter in colour with a slight bluish grey colour compared to healthy spikes.

• Florets may be slightly flared, but have a near normal appearance.

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• Common Bunt and Loose Smut have not been a problem since the middle of the 20th century because of effective control

practices, including the use of seed treatment fungicides and

host resistance.

Significant losses can still occur in individual fields or over small

areas, largely as a result of improper application of control

techniques or complacency.

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Disease Management

• Many of the techniques used to control Loose Smut and Common Bunt are similar.

• Use Resistant Varieties when available.

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Resistance of Barley Varieties Listed in Seed Manitoba

Malting Barley

(26)

Feed Barley

(25)

Hulless Barley

(4) Resistance

Very Good 4 2 3 Good 0 0 0 Fair 5 2 0 Poor 9 17 1

Loose Smut

Very Poor 8 4 0

Very Good 4 10 1 Good 11 8 2 Fair 7 5 1 Poor 3 2 0

Seedling Infecting

Smuts

Very Poor 1 0 0

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Resistance of Oat Varieties Listed in Seed Manitoba

Oats (17)

Hulless Oats (6)

Resistance

Very Good 13 5 Good 0 0 Fair 1 0 Poor 2 0

Seedling Infecting

Smuts

Very Poor 0 0

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Resistance of Wheat Varieties Listed in Seed Manitoba

CWRS CPS

(R) CPS (W)

CWES CWHWS

(35) (6) (1) (5) (2) Resistance

Very Good

6 1 5

Good 14 Fair 8 2 Poor 7 4 2

Loose Smut

Very Poor

Very Good

17 4 1 1

Good 1 1 Fair 13 2 4 Poor 4 1

Bunt

Very Poor

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Resistance of Wheat Varieties Listed in Seed Manitoba

CWSWS CWGP CWAD CWWW (2) (2) (10) (2) Resistance

Very Good

Good Fair 1 Poor 2 1 8

Loose Smut

Very Poor 2

Very Good

2 10

Good 1 Fair Poor 1 1

Bunt

Very Poor 1

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Long Term Natural Infection Experiments

0

1

2

3

4

5

6

Years

1992

1994

1996

1998

2000

2002

2004

2006

Year

Perc

ent I

nfec

tion

Very PoorPoor to FairGood

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Disease Management

• Seed Treatment Fungicides– Highly effective

• Systemic fungicides are necessary for loose smut of wheat and barley• Contact or protectant seed treatments are effective for bunts and the

seedling infecting smuts - Placement is often at the point of infection

– Number on the market• Fungicide resistance – carboxin resistance has been identified

for the loose smut fungi• Fungicide rotations should be practiced. Different modes of

action of the fungicides needs to be stressed.

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Disease Management

• Disease Free Seed– Certified Seed– Embryo Test (Loose Smut)

• Bunts– Crop Rotation – Bunt spores

can survive for 2 years– Seed into warm soils, early

fall or late spring• Seed shallow (4 cm instead

of 7 cm)

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Disease Management

• Hot Water Treatments– 1) Immerse seed in water at 54oC for ½ hour, then cool

immediately.– 2) 20oC water for 5 hours; 49oC for 1 minute; 52oC for 11

minutes; cool water immediately– Need to increase your seeding rate.

Le ChaulageSoak seed in a copper pannier in a mixture of sheep’s urine and milk of lime (portlandite or calcium hydroxide)

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Conclusions

• The smut and bunt diseases of small grain cereals were once diseases of large impact to agriculture

• These diseases are not major problems today because of modern agricultural practices; in particular, the use of resistant varieties and seed treatment fungicides.

• Although these pathogens are of minor importance in modern agriculture, they can be commonly found in western Canada, albeit at low severities.

• Smut and bunt diseases can still cause losses as a result of improper control practices or complacency.

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Thank you!